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Water and Gases

Water and Gases. Pure water (evaporation generally purifies water) interacts with gases in air: Equilibrium between air and gases: H 2 O + CO 2  H 2 CO 3(aq) How do we determine conc. H 2 CO 3(aq) ??. Henry’s Law. A description of gas solubility of gases in solution

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Water and Gases

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  1. Water and Gases • Pure water (evaporation generally purifies water) interacts with gases in air: • Equilibrium between air and gases: H2O + CO2 H2CO3(aq) How do we determine conc. H2CO3(aq)??

  2. Henry’s Law • A description of gas solubility of gases in solution gas(g)↔ gas(aq) O2(g)↔ O2(aq)

  3. What is the difference in O2 at equilibrium with 5ºC water vs. 35ºC water?? • Compare that with SO2…

  4. Gas production? • What processes produce gases? • Degassing from melts • Formation and degassing from metamorphic reactions and hydrothermal systems • Diagenetic reactions, petroleum genesis • Biological production

  5. Oxygenic Photosynthesis Chlorphyll a (P680) is very oxidized (E0=+1.1V), enough to oxidize H2O. BUT e- excitation takes it to E0=-0.7V, not enough to reduce NADP+ to NADPH. Thus a need for 2 photosystems…. Water-oxidizing complex is key – Mn4Ca-complex that oxidizes H2O to O2 in 4 steps (S0 through S4)

  6. Diffusion, Fickian Diffusion from high to low levels.. Where D is the diffusion coefficient, dc/dx is the gradient, and J is the flux of material

  7. Groundwater • Precipitation that does not run-off into rivers percolates into soils, sediments, and into basement rock fractures to become groundwater • Water always flows down-hill • Darcy’s Law describes the rate of flow where,Q = volumetric flow rate (m3/s or ft3/s),A = flow area perpendicular to L (m2 or ft2),K = hydraulic conductivity (m/s or ft/s),l = flow path length (m or ft),H= hydraulic head (m or ft), andd= denotes the change in h over the path L.

  8. Groundwater Chemistry • Just like other waters, encounters minerals, gases, etc. • Some key differences from other waters: • PCO2 variable – respiration! • Segregation of flowpaths in different units

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